But the agency also said the agency wants to work with them to clarify what's legal.
The FDA said Thursday it sent warning letters to five companies that make e-cigarettes or components for the plastic and metal devices that heat a liquid nicotine solution in a disposable cartridge, creating vapor that the "smoker" inhales.
In the letters, the FDA said the companies are violating the Federal Food, Drug and Cosmetic Act, including unsubstantiated claims and poor manufacturing practices.
One of the companies, Las Vegas-based E-Cig Technology Inc., the agency said, is even selling liquid forms of erectile dysfunction and weight loss drugs that can be used in an e-cigarette. The FDA is asking the companies to let the agency know within 15 business days how it plans to correct the violations.
The other companies receiving warning letters are: E-CigaretteDirect LLC of Colorado; Ruyan America Inc. in Minneapolis; Florida-based Gamucci America; and Wisconsin-based Johnson Creek Enterprises LLC.
But in a letter to the Electronic Cigarette Association, the FDA said the actions against the companies were not meant to be seen as a larger effort to ban e-cigs. The agency encouraged the industry group to work with the FDA to ensure the safety and effectiveness of the devices to help people quit smoking traditional cigarettes through usually expensive clinical trials.
"We are interested in finding out whether e-cigarettes can be proven safe and effective," FDA compliance lawyer Michael Levy said in a conference call.
Levy added that there are several FDA-approved smoking cessation aids available on the market and the agency is working with several some manufacturers for approval as a drug-delivery device, but did not provide further details.
Ruyan America, which plans to address the FDA's letter, hasn't offered a product with nicotine for more than a year, said William Bartkowski, the company's president. The company does, however, sell cartridges that contain an herbal ingredient called lobelia, which is marketed to adult smokers as a "tonic," according to a news release on the company's website.
"We appreciate the regulatory ambiguity, and we're just not going to be in the market until such time as that that's cleared up, and that may be a while," Bartkowski said.
Keith King, sales manager with E-CigaretteDirect, said the FDA is misinterpreting language on its website and testimonials from customers as promoting e-cigarettes as a stop-smoking aid. King said while the company will comply, it's "unclear whether the FDA has any jurisdiction" over the products.
"This is another effort on the part of the FDA to control American citizens and take away their freedom of choice," King said.
Representatives with the Electronic Cigarette Association and the other companies issued warning letters did not immediately provide comment.
The battery-powered electronic cigarettes have become the center of a fight over how risky they are compared with traditional smokes, whether they're legal and, if they are, how they should be regulated.
The FDA and public health groups have sounded the alarm, saying they contain dangerous chemicals and are being marketed to children, and the federal agency has halted shipments of e-cigarettes at ports nationwide.
Some sellers of e-cigarettes sued the FDA last year after the agency instructed customs officials to refuse entry of shipments into the U.S. A federal judge ruled that the FDA can't stop those shipments, saying the agency had overstepped its authority. The FDA appealed, and won a stay of that ruling, pending oral arguments that are set to begin later this month.
The FDA would not comment on how Thursday's actions relate to the pending lawsuit.
While the FDA claims it has the authority to regulate e-cigarettes as drug-delivery devices, some sellers contend the products should be regulated as a tobacco product, which would follow the same restrictions as traditional cigarettes and tobacco products.
First marketed worldwide in 2002 as an alternative to regular cigarettes, e-cigarettes didn't become easily available in the U.S. until late 2006.
Now, the industry has grown from the thousands in 2006 to several million worldwide, with estimated 20,000 to 30,000 new e-smokers every week, according to Jason Healy, the president of e-cig maker Blu Cigs, which was not among the companies sent warning letters.